Various systems are presently known which are directed to the rapid or automatic detection of flaws in railroad rails or the like. Such systems are generally directed to the use of automatic or semi-automatic equipment that will detect flaws as a testing vehicle travels along the rail. Due to increasing labor costs, along with increased maintenance requirements, automatic rail detection systems have essentially become mandatory since the cost of manual detection is becoming prohibitive.
One known apparatus used to detect flaws in railroad rails operates on the principal of introducing high frequency (ultrasonic) sound waves into the top or side of the rail and measuring the time period required for the sound wave to rebound from the bottom or opposite side of the rail. Any discontinuity within the rail, or the air/rail interface at the side or bottom of the rail itself, will reflect the sound wave and thus the time it takes for the reflected sound wave to return to a receiver is an indication of a discontinuity (flaw) within the rail or an expected return from the bottom or side of the rail. For example, with a flawed rail, the time required for the high frequency or ultrasonic pulse to rebound is less than would be expected in a normal rail as the occurrence of the flaw causes the ultrasonic sound wave to return earlier than expected since the wave did not travel through the full height or width of the rail.
One ultrasonic rail flaw detection system is described in U.S. Pat. No. 4,004,455 granted to Chester W. McKee et al on Jan. 25, 1977. This system (described in greater detail below) utilizes an ultrasonic transducer mounted in a fluid filled wheel of conventional design and the transducer transmits high frequency sound waves into the rail as the testing car and associated fluid filled wheel travel along the track. The sound waves are reflected within the rail and the return signals are detected and forwarded to counting and other circuitry to detect the presence of flaws emanating from defective areas of the rail. This system, although providing a useful and unique method for automatically detecting flaws in railroad rails is particularly adapted for detecting flaws, in the bolt hole areas of railroad rails during an on-site inspection but lacks the ability to enhance system sensitivity for particular rail areas or segments requiring higher inspection standards.
That is, it is known that railroad companies are instituting tighter specifications for new rails that will allow them to weld rails on site without risking the danger of incurring defects, particularly in the first 18 inches of a rail which forms a heat-affected zone adjacent to the welds. Therefore, from a rail manufacturers standpoint, it has become extremely important that the first and last 18 inches of any rail be inspected with much tighter specifications than the rest of the rail. This is necessary because if any defect, regardless how small, is located within the first 18 inches of the rail when the welding process takes place, those defects, such as slag inclusions, pipe, segregation etc., will literally blow up or expand resulting in premature failure of the rail and/or the weld.
It is, therefore, an object of the instant invention to provide rail inspection equipment with the ability to focus on particular rail segments and increase, at will, system sensitivity in these segments.
It is another object of the instant invention to provide rail inspection capability at the point of rail manufacture to detect potential flaws prior to a rail being delivered to the railroad for installation.
It is a further object of the instant invention to permit increased rail inspection capability for various rail segments with the sensitivity of the testing procedure being variable for each seperate rail segment.
It is a still further object of the instant invention to permit a rail manufacturer to inspect with increased sensitivity, particular rail segments, with the particular segment being inspected, and system sensitivity for that segment, being subject to operator control.
Yet another object of the instant invention is to provide such improved rail inspection apparatus which is readily fabricated at low cost from commercially available components.